A rather simple question, but I can't work out how to convert a nested loop of such a kind:
for (var a = 0; a < n; a++)
{
for (var b = a + 1; b < n; b++)
{
//let here be a creation of a Tuple
list.Add(Tuple.Create(a, b))
}
}
to a LINQ-statement
upd:
I tried something like this:
from a in Enumerable.Range(0, n)
from b in Enumerable.Range(1, n)
...
but it didn't work
Alright, here is one solution using Linq extension methods.
var list = Enumerable.Range(0, n-1)
.SelectMany(
a => Enumerable.Repeat(a, n-1 - a)
.Zip( Enumerable.Range(a+1, n - (a+1)) )
).ToList();
How does it work? Well, look up the documentation for the involved Linq methods, that should provide sufficient insight to what's going on here with that ugly Linq construct of mine. (Well, it's not only ugly, it's also so slow you are not at any risk of violating any speed limit...)
Note that the generated list is of type System.Collections.Generic.List<(int First, int Second)>, which is using C# tuples, which are a value types and not to be confused with the System.Tuple type (which is a reference type) you used in the code in your question.
And here is a solution involving Linq query syntax:
var list = (
from a in Enumerable.Range(0, n - 1)
from b in Enumerable.Range(a + 1, n - (a + 1))
select (a, b)
).ToList();
It could be helpfull.
var result = (from a in Enumerable.Range(0, n - 1)
from b in Enumerable.Range(a + 1, n - a - 1)
select Tuple.Create(a, b)).ToList();
Tuple.Create will return Tuple instead of ValueTuple and should be avoided for new code due to unnecessary memory pressure. Instead, just select (a, b). EDIT: I see you were basing your code on the OPs question. I've replicated the comment in the OP.
You may use this:
Enumerable.Range(0, n-1).ToList().ForEach(x => Enumerable.Range(x + 1, n-x-1).ToList().ForEach(y => list.Add(Tuple.Create(x,y))));
list.AddRange(resultOfUsingLinq)? In any case, I love LINQ, but I have serious doubts you're going to end up with a LINQ solution that is going to be easier to read than what you have with your loops.